We propose to extend previous work in developing and evaluating innovative interventions that help individuals adopt and maintain physical activity regimens. There is a need for effective interventions to promote physical activity since only 32percent of U.S. adults engage in regular leisure time physical activity. In our parent trial (HL64342), we tested an individually tailored, theory-based physical activity promotion intervention in print versus telephone delivery channels. We found the print delivery channel to be superior to the phone delivery channel at 12-month follow-up. Participants in the print arm increased their weekly participation in physical activity from an average of 19 minutes at baseline to an average of 129 minutes at 6 months and 167 minutes at 12 months (significant increases relative to controls), consumer satisfaction data revealed that participants found the program to be acceptable, and 87 percent of participants returned for the 12- month follow-up assessment. However, despite these large increases in physical activity behavior only 40 percent of the sample at 6 months, and 50 percent of the sample at 12 months, had achieved the recommended 150 minutes per week of moderate intensity physical activity. In the proposed study we aim to test an enhanced version of our individually tailored print intervention in an attempt to help a larger percentage of participants achieve the national recommendations for physical activity participation endorsed by the Centers for Disease Control and Prevention, the American College of Sports Medicine, the National Institutes of Health, the Surgeon General, and the American Heart Association. Thus, we will conduct a randomized controlled clinical trial to determine the differential effect of the print-based individually-tailored intervention used in our parent trial (tailored print) vs. an Enhanced print- based individually-tailored intervention (Enhanced tailored print) on physical activity adoption and short-term maintenance in previously sedentary adults. Two hundred and forty healthy, sedentary women and men ages 18-65 will be randomly assigned to one of the two interventions. Data will be collected at baseline, 6, and 12 months using well-established physical activity and physical performance measures, as well as a comprehensive set of psychosocial questionnaires. We hypothesize that significantly more individuals in Enhanced tailored print will meet the public health recommendations of accumulating at least 150 minutes of at least moderate intensity exercise per week than those individuals in tailored print. Additional questions of interest include examination of potential moderators and mediators of the intervention-physical activity relationship and evaluation of the cost-effectiveness of the two interventions. This study will contribute important information regarding ways to increase the number of participants who achieve the physical activity guidelines and will thereby yield important information regarding the prevention of CVD.